Field of the Invention
The present invention relates to a wafer processing method of processing a wafer to form a plurality of device chips with a die-bonding resin provided on the reverse sides thereof.
Description of the Related Art
In the step of fabricating semiconductor devices for use on ICs (Integrated Circuits), LSI (Large Scale Integration) circuits, etc., a wafer with a plurality of devices disposed in areas demarcated by projected division lines and formed on its face side is divided into individual device chips, thereby producing semiconductor device chips. The semiconductor device chips are then packaged for use in electric devices such as mobile phones, personal computers, etc.
The semiconductor device chips are bonded to lead frames (metal boards) or the like. There is known in the art a step of laying a bonding material for bonding the semiconductor device chips to lead frames on the reverse sides of the semiconductor device chips. According to the known step, a DAF (Die Attach Film) which is of approximately the same size as the wafer is applied to the reverse side of the wafer prior to its being divided into individual device chips, and then the wafer is divided into individual device chips by a cutting blade that cuts into the face side of the wafer. At the same time, the bonding material on the reverse side of the wafer is also divided into pieces corresponding to the individual device chips. In this manner, the individual device chips are separated and taken from the wafer as semiconductor device chips each with the bonding material on its reverse side. Reference may be made to Japanese Patent Laid-Open No. 2000-182995, for example.
The above method of laying the bonding material is based on the premise that the wafer is ground (thinned) to a desired thickness from the reverse side thereof, and then the DAF is applied to the ground reverse side of the wafer, after which the wafer is diced from the face side into the individual device chips. However, if there is employed a technology referred to as “dicing before grinding” wherein a dicing step is carried out on face side of a wafer by a cutting blade to form separation grooves having a depth corresponding to a finished thickness and thereafter the reverse side of the wafer is ground to divide the wafer into individual device chips, then it is difficult to rely on the above laying method because the wafer is divided into individual device chips at the same time that the grinding of the reverse side of the wafer is completed.
For laying a bonding material, e.g., a die-bonding resin, on the reverse sides of device chips in the “dicing before grinding” step, attempts have been made to apply a die-bonding resin film to the entire reverse side of a wafer after the wafer is diced into individual semiconductor device chips and before the individual semiconductor device chips are taken from the wafer, and to apply a laser beam to the wafer from the side of the separation grooves in the face thereof, thereby dividing the die-bonding resin film into pieces corresponding to the semiconductor device chips (see, for example, Japanese Patent Laid-Open No. 2002-118081). The separation grooves whose depth corresponds to the finished thickness of the device chips may be formed along the projected division lines by etching or the like, rather than the cutting blade (see, for example, Japanese Patent Laid-Open No. 2006-294913).